The innovation relates to a mounting means for a wheel-revolution sensor in the wheel support of a motor vehicle, for scanning a revolving pole ring, said mounting means comprising an insert which passes through a bore in the wheel support and into which the sensor is designed to be pushed on that side which faces away from the pole ring.
Wheel-revolution sensors, in particular passive inductively operating sensors for motor vehicles, are usually placed in a protective insert, as indicated in DE 37 03 395 A. In this regard, a spring cage is usually used, and the sensor is pushed directly against the pole ring. As a result of the bearing play of the rotating parts which support the pole ring and as a result of the out-of-roundness of the pole ring, the sensor is then slightly pushed in an outward direction. This results in a gap of about 0.2 mm in the mounted state.
In view of the fact that, due to the construction, the bearing play increases in the course of the service life, the clamping force of the spring cage is to be dimensioned such that the sensor, when making contact with the pole ring, is pushed out slightly, but not damaged spacing at which still just usable pulses are generated is about 0.8 mm Yet, since the amplitudes are also low precisely when detecting the drive slip when starting-up (low frequencies), while accurate measuring is required, it is necessary for this spacing to be kept to a minimum.
Specifically with regard to all-terrain vehicles, incidents do occur in which mud particles and gravel are caught between the pole ring and the sensor, pushing the sensor out of its position. In so doing, the spacing between the sensor and the pole ring is increased beyond the operative range. Filling the tooth gaps of the pole ring with non-metallic material (e.g. EP 597 378 Al) also does not afford relief. In front of the sensor, a mud cake may build up and either push out the sensor or, if it hardens or freezes, damage the sensor.
The foregoing object is achieved wherein an insert is provided with a limit stop for the sensor in the fully inserted position, and in that, in this position, that edge of the insert which faces the pole ring projects beyond the sensor.
The limit stop determines the optimal position; the projecting edge protects the senior, such that it is no longer necessary to tolerate the expulsion of the sensor upon contact.
In a particularly advantageous further development of the innovation, that edge of the insert which faces the pole ring is provided with recesses in the sectors beyond the zone which is swept by the pole ring. These recesses, which are disposed laterally relative to the circumerential direction of the pole ring, ensure the lateral discharge of earth particles, which were squeezed through by the pole ring under the edge, it being possible for said particles to fall out laterally, thereby preventing an accumulation of material under the sensor, as a result of which it would otherwise by pushed outwardly.
In a further development, two recesses are provided in the sector, in the circumferential direction of the pole ring in each case one upstream and downsteam of the point of the greatest breadth of the sector. As a result hereof, the sensor remains protected against interference from the side, while it is possible for the two respective recesses to be shaped and arranged in an optimal manner in respect of the two directions of rotation.
In one optional embodiment, the limit stop is designed to be a shoulder in the interior of the insert, while in another optional embodiment it is designed to be an inwardly directed projection of the edge of the point of greatest breadth of the sector. Accordingly, the limit stop is arranged laterally of the zone swept by the pole ring, thereby also complementing the self-cleaning effect of the insert.
In a further development, two recesses are provided in the sector, in the circumferential direction of the pole ring in each case one upstream and one downstream of the point of the greatest breadth of the sector. As a result hereof, the sensor remains protected against interference from the side, while it is possible for the two respective recesses to be shaped and arranged in an optimal manner in respect of the two directions of rotation.
In further developing the embodiment comprising the limit stop which is designed to be a shoulder in the interior of the insert, the head of the sensor is positioned between a spring ring, supporting an O-ring, and the shoulder.
In an alternative embodiment, the sensor is held in its lowermost position by means of a bracket.